People make their way past mailboxes outside a closed Hellenic Post branch in Athens, Greece, March 20, 2017. REUTERS/Alkis Konstantinidis

Greek police intercepted eight suspect packages at a postal sorting center in Athens on Monday, after the dispatch of booby-trapped deliveries to the International Monetary Fund in Paris and the German Finance Ministry.

Authorities were on the lookout after the two packages laced with gunpowder slipped through checks last week. A Greek urban guerrilla group that sent letter bombs to foreign embassies in Athens and European leaders in 2010 is thought to be behind the attacks.

A package containing a book concealing the explosives and addressed to German Finance Minister Wolfgang Schaeuble was intercepted by German authorities. A letter addressed to the International Monetary Fund in Paris, exploded, slightly hurting an administrative assistant.

"Eight suspect packages which listed as recipients persons in European countries were located and confiscated today," police said in a text message to journalists.

It did not specify who the recipients were. A security source said they were "addressed to officials at economic institutions and companies" at various European countries but would not be more specific.

A Greek militant group, Conspiracy of Fire Cells, had claimed responsibility for the first suspect package sent to Germany and intercepted on March 15.

It has not claimed responsibility for the letter to the IMF that exploded on March 16, but authorities assume the same group is behind it.

In both cases, the packages listed as senders members of the New Democracy opposition conservative party.

Greece has a long history of urban guerrilla group attacks.

Conspiracy of Fire Cells initially conducted arson attacks but turned to bombings in 2009. The group has become prominent since the economic crisis erupted in Greece and is accused by police of carrying out more than 150 criminal acts.

In a proclamation in November, the group said that its plan, which it called "Nemesis", was designed to "spread fear into the yards of the homes of our enemy". The group called sending the explosive parcel to Germany "Nemesis- Act 2".